The present invention relates to a tracking method, which is set up for position determination in an interior space.
The tracking method according to the invention determines the position of a mobile measuring station relative to a base station in an interior space. The tracking system has a base station and a mobile measuring station. The position of the measuring station is determined relative to the base station. The base station swivels or rotates a bundle having at least one light beam about at least one axis of the base station in emission directions that change according to a predefined process to generate a migrating pattern of points of light on a wall of the interior space. A camera of the mobile measuring station records a series of images of the wall of the interior space under a uniform viewing direction, wherein in the series, one of the migrating points of light is imaged on at least three different image points. The image coordinates of at least three different image points are determined. At least three emission directions of the light beams, whose points of light are imaged, at one point in time in one of the images, on one of at least three different image points, are determined based on the instants at which the respective image is recorded. At least three distances of the base station axis to the wall in at least three emission directions are determined based on distance-to-the-wall measurements, stored in a reference database, in measurement directions originating from the base station. The position of the mobile measuring station is determined based on the image coordinates of at least three image points, the emission directions associated with the image points, and the respective distances of the base station to the wall in the associated emission directions.
The bundle may consist of exactly one light beam or multiple light beams arranged in constant angular distances to each other. The series may comprise one or multiple images, which are characterized by the same viewing direction. For a series of different images, one can image the point of light of a light beam on various image points or one can image points of light of various light beams on the various image points.
The distance measurements in the measurement directions occur preferably with a measuring light beam of an optical distance measuring unit. The tracking method may have an initialization phase that is separate from a tracking phase. During the initialization phase, at least one measuring light beam is rotated or swiveled about at least one axis in measuring directions that change according to a predefined sequence. The respective distance of the axis to the wall in the measuring directions is measured based on a duration and/or interference measurement of the measuring light beam. The measuring directions and associated measured distances may be stored in a reference database. During the tracking phase, the distance in an emission direction of the light beam is determined by means of a measuring direction corresponding to the emission direction in the reference database or a mean value of the stored distances weighted according to the respective differences of the stored measurement directions to the emission direction.
One design provides that during the initialization phase, the measuring light beam is rotated or swiveled at a first angular velocity, and during the tracking phase, the bundle of light beams is rotated or swiveled at a second angular velocity, wherein the second angular velocity is greater than the first angular velocity.
One design provides that the sequence according to which the bundle with at least one light beam is rotated or swiveled, is identical to the sequence according to which the measuring light beam is rotated or swiveled.
One design provides that the bundle is rotated or swiveled about precisely one axis and the bundle has at least two light beams, which are angled to each other at an angle in a plane containing the axis. The base station moves the bundle about a vertical axis for example, and through the movement and instants, it achieves a horizontal resolution. The vertical resolution is obtained by the resolution of the light beams in various elevation angles. The vertical resolution is limited by the number of light beams and significantly less than the resolution, limited by the time measurements, in the horizontal plane. However, the structures of typical interior spaces exhibit comparatively fewer changes along the vertical direction in comparison to the horizontal directions.
One design provides that a first one of the images is taken at a first instant and a second one of the images is taken at a second instant different from the first instant. The first instant can be adaptively adjusted to image one of the points of light of the migrating pattern on an image point at the edge of the image, and the second instant is adaptively adjusted to image one of the points of light of the migrating pattern on an image point at another edge of the image.